This invention concerns a device for the determination of the location of a warp thread break in weaving looms using drop wires.
In conventional warp thread control systems, the use of a drop wire to locate warp thread breaks is already well known. In such a system, a drop wire is associated with each warp thread in such a way that, in case of a break of a warp thread, the corresponding drop wire is caused to fall downwards onto an electrode common to all the drop wires, whereby an electrical circuit is closed resulting, finally, in stopping the weaving loom. According to an alternative solution described by the French Pat. No. 982,218 and the German Pat. No. 801,920, the detection of a fallen drop wire is achieved by means of one or several photo-electric elements. Because of the large density of the warp threads, i.e., 40 to 60 threads per centimenter, it is quite obvious that the pack of drop wires associated with the threads is very dense and compact. In order to facilitate the associating of each warp thread with a drop wire, the drop wires are distributed in five to six rows across the warp threads. Quite obviously, such a large pack of steel drop wires constitute a non-transparent system in which it is quite difficult to look through to the underside of the five to six rows of drop wires because sight is obstructed by the plane constituted by the warp threads. This type of installation has the disadvantage that, while the repair of a warp thread break is carried out, 30 to 50% of the time required for the repair is spent on detecting the fallen drop wire. The machine operator of the loom must leave his station in order to look under the drop wire pack and manually determine the exact location of the fallen drop wires.
A known solution permitting a quicker location determination of the fallen drop wires is disclosed in German Pat. No. DOS 1,535,597, whereby the drop wires or other contact elements completely fall out of the pack of drop wires and are collected ina relatively well visible gutter. In such an installation the location of the broken warp thread is indicated relatively well, but it has the disadvantage that it is quite difficult to exactly determine the location where the drop wire, which has completely fallen out of the drop wire pack, must be picked up. Errors are thus by no means eliminated in this system.
The second known solution of the problem of location determination of a warp thread break involves the distribution of contact electrodes for all the drop wires into zones whereby, by means of a warning lamp, a zone where a fallen drop wire is present can be indicated. In this system, the disadvantage of the necessary manual search is still present.
According to a third solution of the problem as suggested by U.S. Pat. No. 3,725,911 and by Japanese Pat. No. 60-81355, the zones could be still further sub-divided, and each drop wire could be associated with an electrode or a contact element or similar system with a corresponding indication element. Bearing in mind the large number of fine electrodes which would be required in such a system, this solution would be a very expensive and unpractical one. Additionally, contacts of this kind are quickly contaminated by dust present in the weaving loom.